drm/amd/display: Get cache window sizes from DMCUB firmware

[Why]
Firmware state and tracebuffer shouldn't be considered stable API
between firmware versions.

Driver shouldn't be querying anything from firmware state or tracebuffer
outside of debugging.

Commands are the stable API for this once we have the outbox.

[How]
Add metadata struct to the end of the data firmware that describes
fw_state_size and some reserved area for future use.

Drop the tracebuffer and firmware state headers since they can differ
per version.

Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>